Purpose — to study the effect of insulin therapy on the concentration of vascular endothelial growth factor A (VEGF-A) in the intraocular fluid of rats with alloxan model of diabetes mellitus. Material and methods. The experiment was conducted on 80 mongrel rats. In 65 rats, the alloxan model of diabetes mellitus was simulated by a single intraperitoneal injection of 100 mg/kg alloxan hydrate saluted in 0.4 ml of citrate buffer. 72 hours after intraperitoneal administration of alloxan monohydrate, these animals were divided into 2 groups. The main group (group 1) consisted of animals with alloxan model of diabetes mellitus, who started daily single intraperitoneal administration of prolonged-acting insulin at a therapeutic dose of 0.9 U/kg Body weight. The comparison group (group 2) consisted of animals with alloxan model of diabetes mellitus who did not receive specific therapy. 15 healthy rats constituted the control group (group 3). Experimental animals were removed from the study on day 31 of insulin therapy. The concentration of VEGF-A was determined in 80—90 μl of intraocular fluid collected from both eyes of each animal. Results. In the main group, the median of VEGF-A concentration [25th; 75th percentiles] in the intraocular fluid was 140 [136; 210] pg/ml, which is 1.94 times higher than in the comparison group (72 [58; 86] pg/ml) and 1.84 times higher than in the control group (76 [62.5; 88] pg/ml). The concentration of VEGF-A in the intraocular fluid in the main group was statistically significantly higher, as compared with the comparison group (pm—u<0.0004), and compared with the control group (pm—u=0.0045). The comparison group had no statistically significant differences when compared with the control group (pm—u=0.9979). Conclusion. Insulin therapy for 31 days increases the concentration of VEGF-A in the intraocular fluid of rats with alloxan model of diabetes mellitus.